The electron carrier effective in nitrite reduction in proplastids of cultured tobacco cells has been purified by DEAE-cellulose and Sephadex G-100 chromatography. Its electron carrying activity in the nitrite reduction system with dithionite showed that 355 nmol NO2−reduced mg−1protein min−1. The electron carrier had absorption maxima at 419, 459 and 469 nm, and the absorbance peak at 419 nm was decreased 56on reduction. The reduced form of the electron carrier showed an electron paramagnetic resonance signal with g=1.93. Thus, this electron carrier is a kind of ferredoxin. It did not, however, show electron carrying activity in the NADP-photoreduction system of chloroplasts. Its molecular weight was calculated as 19,500 by Sephadex G-100 chromatog
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